1. Field of the Invention
The present invention relates to a speaker with a built-in direct current (DC) motor, and more particularly, to a speaker with a built-in direct current (DC) motor that is provided in portable equipment such as a cellular phone generating vibration, thereby selectively outputting sound and/or vibration.
2. Background of the Related Art
FIG. 1 is a partial view illustrating a cellular phone with a conventionally used micro speaker and a coin type vibration motor embedded therein.
Recently, consumers desire to purchase a cellular phone that has the functions of producing at least 16-chord or 40-chord polyphonic ring tone and displaying colors. This needs a micro speaker having a range of 17 Phi or more. Since the micro speaker and a vibration motor are separately made for use in conventional cellular phones, however, they should be provided individually in the interior of the cellular phone. As shown in FIG. 1, a cellular phone 3, which has basic specifications of black and white LCD and 16-chord or less sound output, needs a substantially large area for installing a vibration motor 2 and a micro speaker 1 therein. Also, in order to add the functions of providing the micro speaker with a range of 17 Phi or more and displaying colors, there is a need for ensuring a relatively large area within the cellular phone 3.
To solve this problem, there has been provided a micro speaker itself having a vibration function by Korea and Japan in recent years.
The configuration of the conventional vibration speaker will be described in detail hereinafter with reference to FIG. 2.
FIG. 2 is a sectional view of the conventionally used vibration speaker.
Referring to FIG. 2, a lower plate 10 is provided with an air hole 11 from which a sound is generated, in the center thereof and with a vibration plate 12 that is spaced apart by a predetermined distance therefrom on the upper portion thereof in such a manner as to be vibrated by means of a plurality of first elastic support parts 14. The vibration plate 12 is provided with a pair of coils 13 facing with each other on the upper portion thereof, each of which is in the shape of a generally semi-arc. There is also provided an upper case 15 for covering the upper portion of the lower plate 10. The upper case 15 is provided with a magnet 16 that is disposed on the bottom surface thereof to correspond to the pair of coils 13 in such a manner as to cover the pair of coils 13. And, the upper case 15 is disposed on the upper portion of the lower plate 10 in such a manner as to be able to be vibrated by means of a plurality of second support parts 17.
A reference numeral 18 denotes a generally flexible cover that is adapted to connect the outer peripheries between the lower plate 10 and the upper case 15, such that it prevents foreign materials from entering a space between the lower plate 10 and the upper case 15.
In operation, when an alternating current (AC) having a low frequency is applied to the pair of coils 13, the polarities of the coils 13 and the magnet 16 disposed on the bottom surface of the upper case 15 are in turn opposite to each other, such that the upper case 15 and the magnet 16 are in a seesaw situation (the left and right parts on the drawing move up and down) relative to the center of the magnet 16 on which the two polarities meet, thereby making it possible to generate vibration.
However, the above-mentioned vibration speaker has the following problems: first, the alternating current of the low frequency corresponding to the resonance frequencies of the first and second elastic support parts 14 and 17 should be applied to said vibration speaker; and second, the elastic modulus of the first and second elastic support parts 14 and 17 are varied over time, such that the frequency of the alternating current applied has should be appropriately varied. That is to say, the first and second elastic support parts that are vibrated when the alternating current having a frequency of about 147 Hz is applied to the pair of coils 13, but as a predetermined period of time passes, they may not be vibrated due to the variation in their elastic modulus. Therefore, there is a need for a driving part for use in the vibration speaker that expects the variation of the elastic modulus with the lapse of time to convert the initially applied alternating current into the alternating current having a frequency corresponding to the expected elastic modulus variation.
Accordingly, the present invention is directed to a speaker with a built-in DC motor that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a speaker with a built-in DC motor that has a coin type DC motor embedded in a micro speaker for generating vibration therein, thereby selectively generating sound and vibration.
Another object of the present invention is to provide a speaker with a built-in DC motor that is capable of achieving the miniaturization of portable equipment having a micro speaker by decreasing the space in the portable equipment occupied by a conventional micro speaker and coin type vibration motor.
Another object of the present invention is to provide a speaker with a built-in DC motor that is capable of maintaining its initial performance for a relatively long period of time, without having an additional driving part.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
According to an aspect of the present invention, there is provided a speaker with a built-in direct current (DC) motor embedded therein for selectively generating sound and vibration, the speaker comprising: a speaker part including; a yoke having a hole formed at the center thereof, a first ring-shaped magnet mounted on the top surface of a peripheral portion of said yoke in such a manner as to be positioned coaxially with the center axis of said yoke, a ring-shaped upper plate mounted on the top surface of said first magnet in such a manner as to be positioned coaxially with the center axis of said yoke, and adapted to form a magnetic gap between a bent portion of said yoke and said upper plate to thereby constitute a magnetic circuit for generating magnetic flux together with the yoke and the first ring-shaped magnet, a vibration plate attached to the top surface of said upper plate at the circumferential end thereof in such a manner as to be positioned coaxially with the center axis of said yoke, and a generally cylindrical voice coil attached to the bottom surface of said vibration plate and inserted into said magnetic gap, a direct current motor part including; a first lower plate fixedly attached to the bottom surface of said peripheral portion of said yoke, a flexible printed circuit board disposed on said first lower plate, and having a hole formed at the center thereof and a brush transmitting a driving signal, a second ring-shaped magnet mounted on the top surface of said first lower plate in such a manner as to be positioned coaxially with the center axis of said yoke, a rotary shaft fitted at one end thereof into said hole of said yoke and fitted at the other end thereof into said hole of the center of said flexible printed circuit board, and an eccentric rotor rotatably mounted on said rotary shaft and adapted to rotate in response to the driving signal generated from said brush; and a frame adapted to support said speaker part and said direct current motor part.
Preferably, the frame may have a flexible printed circuit board mounted on one side thereof, the flexible printed circuit board having a power feed terminal electrically connected to the voice coil and the brush connected to the eccentric rotor, respectively, and adapted to supply a driving signal to the voice coil to generate sound and a driving signal to the brush to generate vibration due to the rotation of said eccentric rotor.
Preferably, the direct current (DC) motor further includes a motor""s upper case which has a hole at the center of an inner surface thereof and contains said rotary shaft having an one end thereof fitted into said hole, said rotor and said second magnet; and a motor""s lower case which is connected to the bottom of said upper case and has said second magnet thereon, such that said direct current motor is placed in a space defined by the bottom surface and the inner lateral walls of the central portion of said yoke and the top surface of said lower plate.